The Olds block being machined for bronze lifter bore bushings and a reduction from the .921" oem size to .842" to make lifters much easier to find. BTR Performance in Rochester, NY did this special operation.

This shows the front of the block machined to accept a Torrington bearing between the camshaft timing gear and the block to reduce friction and front to rear movement of the camshaft. Another operation by BTR Performance.